This invention relates to apparatus for examining a body by means of penetrating radiation, such as X- or .gamma.- rays, to obtain the distribution of absorption coefficients with respect to the radiation in a plane passing through the body.
Such apparatus, hereinafter termed apparatus of the type described, is disclosed in U.S. Pat. Nos. 3,867,634 and 3,946,234. These patents disclose, respectively, a rectangular yoke and a C-shaped yoke which is slidably mounted on a support structure for bidirectional translation in a plane parallel to a circle of reconstruction within which a body to be examined is located. Rigidly attached to the yoke is a radiation beam assembly including a radiation source located on an arm of the yoke on one side of the center of the circle of reconstruction for producing a collimated beam of penetrating radiation, and detector means located on the opposite arm of the yoke for receiving radiation from the source passing through the circle of reconstruction. The structure is mounted for rotation about the center of the circle of reconstruction so that a body therein is scanned linearly by the collimated beam during translation of the yoke and at many different angles as the structure is rotated. The data produced by the detector means are processed in a computer in a known manner to provide the distribution of absorption coefficients over the plane of the circle of reconstruction.
The rectangular or C-shaped yoke provides a rigid mechanical coupling between the source and the detector means which maintains a fixed spatial relationship therebetween during translation of the radiation beam assembly on the support structure. Such relationship is critically important because relative displacement between the source and the detector means degrades the computed distribution of absorption coefficients. As a consequence of the geometrical considerations requiring a large radial dimension of the yoke, special designs must be resorted to in order to accomodate the resultant dynamic loadings due to the high accelerations experienced during the linear portion of the scanning operation as efforts are made to reduce scanning time.
Until the present, it has not been possible to reduce the physical size and mass of the coupling between the source and the detector means while maintaining the required rigidity therebetween during linear scans. It is therefore an object of the present invention to provide, in apparatus of the type described, new and improved coupling means which are more compact than the prior art, and which involves less mass and provides more favorable static moments than the coupling means of the prior art.